A few years ago, I switched back to a Mac after a 15 year hiatus. Overall, it was a positive experience. And overall, I prefer the Mac OS X Leopard to Windows XP. I have no experience with Vista, so I can't comment on that. But given my general tendency of complaining and my annoyance of religiously fervent Mac fans, I feel I should share a few things that, in my opinion, represent poor usability design in the Mac.
Now there is no way to gauge how skewed my opinions are by the fifteen years of Windows experience. Sometimes people judge something as crappy just because it is new to them. As a teacher, I see this in my students. Most people taking my class are moving from an old technology to a new technology. And many of my students complain that the "new way" of doing things sucks and that their "old way" (in Cobalt, Fortran, PowerBuilder, etc) was much better. Sometimes, they are right. But sometimes, they just haven't gotten used to the "new way". Its probably impossible to separate "poor design" from "I'm just not used to it", but none-the-less, I'll try.
#1 Context Insensitive Menus
Most Mac applications have a global menu bar. And this is how you access most of the app's functionality. What's more, the menu is anchored to the top of the screen. Not the top of the document. Not the top of the panel - the top of the computer screen. This, in my opinion, isn't just different from what I am used to. It's a poor design. It violates the UI design Principal of Context. Most user actions apply to a specific context (i.e. object): a paragraph, the selected cells, the current document, etc. This is the fundamental concept of OO (an object is really just a context). Imagine you have a dual monitor setup. You have a graphics application running on the right screen. And you want to modify a rectangle. Where do look for a list of possible actions? The rectangle? No. The document? No. You look to a menu bar at the top of your left monitor. The only argument, in favor of this design is that it saves a bit of screen real estate. And old Mac people are used to it. But, overall, in my opinion it is just poor usability design.
#2 No Maximize Button
Mac windows do not have a maximize button. They have something kind-of (but not really) comparable: the Zoom Button. It is one of the 3 tiny circle buttons in the upper left corn of every Mac window. The zoom button attempts a "size to fit". Most UI programming toolkits have a function like this built-in. In Java Swing, it's called the pack() function. Basically, the window attempts to find the optimal size (not too big, not too small) based on the window's contents. The problem with this approach is that the algorithm is wrong most of the time. And it takes control away from the user. Often, when browsing with Safari, I just want the whole screen. Obviously, it's not a deal breaker. I can just drag the window bigger if needed. It's just a pain in the butt. By the way, many (non apple) vendors simply have their zoom buttons do a maximize. But Safari, Finder and iTunes do not.
#3 The Window Buttons
Most windows on my Mac have 3 buttons in the upper left corner (one of them is the Zoom button mentioned above). These buttons are just circles. There is no indication of what they do. If you hover your mouse over the button, then an image appears. But you get no tool tip telling you (in words) what the button does. This, in my opinion, is not just different from what I am used to. It's just poor usability design. Why not just have the image visible all the time? Why not have a tool tip? Perhaps some designer thought it looked prettier this way. I don't know.
I think Apple is great at creating interfaces that look great. But as far, as usability goes, I think they are probably good. Above average. But not great. At least not based on my Mac experience.